As such prior art example, the following system is proposed. Basically, the system has: a distributing recording medium such as a CD-ROM on which encrypted digital content are recorded; management means for managing a charge for use of the digital content of a user; and a digital content playing device which is a device used for playing the digital content by the user who has obtained the distributing recording medium and can be connected via the Internet line to the management means, wherein when a request to play the digital content under authentication and charging conditions is inputted by the user to the digital content playing device, the digital content playing device transmits the request via the Internet line to the management means, the management means checks authentication and charging of the user related to the request to transmit decryption key data via the Internet line to the digital content playing device, and the digital content playing device uses the decryption key data to decrypt and play the digital content on the distributing recording medium (for example, see Patent Document 1). “Patent Document 1: Japanese Patent Application Laid-Open No. 2002-334172”
In the above prior art example, however, when the digital content on the distributing recording medium are once decrypted by the digital content playing device, the digital content can be not only played but also easily copied. There is an essential disadvantage that secondary unauthorized use cannot be prevented.
Although addition of a function of automatically deleting the digital content when a predetermined period has elapsed from the play request can at least prevent the secondary unauthorized use, there is another disadvantage that collection of a charge for the secondary use cannot be expected. This is not a specific problem faced only when distributing the digital content via the distributing recording medium to the user, and is alike when delivering the digital content via the Internet line to the user. The advantage to be originally obtained by such as a content holder is lost in an unauthorized manner. In this point, under the current circumstances, the distribution of the digital content is prevented from being promoted.
The present disclosure has been made under the above background and an object of the present disclosure is to provide a system for preventing unauthorized use of digital content which can prevent unauthorized use of digital content and can reliably collect a charge for secondary use.